1. Field of the Invention
The present invention generally relates to a transceiver, and more specifically to a transceiver for a radio frequency identification (RFID) reader.
2. The Prior Arts
Nowadays, RFID has been widely used in various fields. In a traditional RFID reader of an RFID system, the analog front end (AFE) has a complex structure with a large circuit size, large power consumption and high cost. FIG. 1 is a block diagram illustrating a transceiver 11 of a traditional RFID reader 1. Referring to FIG. 1, the AFE 12 of the transceiver 11 of the traditional RFID reader 1 includes a pair of mixers 13 (i.e., an I-channel mixer 131 and a Q-channel mixer 132), a pair of dense reader mode (DRM) filters 14, a pair of inputting gain circuits 15, a pair of digitizers 16, a received signal strength indication (RSSI) measuring means 17 and an outputting gain circuit 18.
An RF signal RFS from an external device (such as an RFID tag) which is received by the RFID reader 1 is sent to a directional unit 19 and then sent to the pair of mixers 13. The received RF signal RFS is down-converted to an I-channel baseband signal IBS and a Q-channel baseband signal QBS by the pair of mixers 13, and the pair of DRM filters 14 eliminates undesired noise and harmonic components. Furthermore, the pair of inputting gain circuits 15 amplify the I-channel baseband signal IBS and the Q-channel baseband signal QBS. Subsequently, the amplified I-channel and Q-channel baseband signals are converted to digital signals IDS and QDS by the pair of digitizers 16. The digital signals IDS and QDS are sent to an MCU for post processing. On the other hand, the amplified I-channel and Q-channel baseband signals are also sent to the RSSI measuring means so as to measure RSSI and thereby detect interference from other external devices.
However, the pair of mixers 13, DRM filters 14 and inputting gain circuits 15 consume relatively large power, have large circuit size and high cost, which in turn results in a large overall size and high cost of the transceiver 11 of the RFID reader 1. Further, in order to accommodate large power consumption, the RFID reader 1 may require an external power supply, such as a battery. Accordingly, such an RFID reader 1 is not suitable for a portable device.
It may therefore be desirable to have a transceiver for an RFID reader which has a simple structure, small size and low power consumption, which is suitable for a portable device.